Light-emitting diodes are power-saving and highly-efficient light sources. Based on different wavelengths of emitted light, light-emitting diodes can be applied to lighting, backlights in displays, and traffic indicators, etc. The demand for cost/performance (C/P) value and the brightness per unit area of light-emitting diodes is getting higher due to the wide applications of light-emitting diodes.
A conventional light-emitting diode comprises a substrate, a light-emitting semiconductor stack on the substrate, a first electrode on the light-emitting semiconductor stack and electrically connected to the light-emitting semiconductor stack, and a second electrode on a surface of the substrate opposite to the first electrode and electrically connected to the light-emitting semiconductor stack. The first electrode comprises a first layer proximal to the light-emitting semiconductor stack and a second layer on the first layer, wherein the second layer comprises an adhesion layer comprises Ti or Cr for increasing the adhesion between the first layer and the second layer. However, elements such as Ti or Cr are easy to be oxidized and thus form metal oxides due to the moisture in the environment, and such chemical reaction of the elements results in deterioration of the adhesion layer, and the deterioration further leads to a peeling problem between the first layer and the second layer.
The above light-emitting diode can be combined with a submount to form a lighting device. The lighting device comprises a submount with a circuit; a solder on the submount, by which the above light-emitting diode can be fixed on the submount, and the substrate of the above light-emitting diode is electrically connected to the circuit on the submount; and an electrical connection structure for electrically connecting the pads of the light-emitting diode and the circuit on the submount; wherein the above submount could be a lead frame or a large mounting substrate for facilitating the design of the electrical circuit of the lighting device and increasing the heat dissipation efficiency.